Cboe reports record $146B in S&P 500 box spread trades as investors flee Treasuries

The S&P 500 options market has quietly become one of the hottest corners of fixed income. Cboe Global Markets reported that outstanding notional value in SPX box spread trades hit $146 billion as of mid-September 2026, an all-time record that underscores just how aggressively investors are looking for alternatives to a deteriorating Treasury market. Average daily notional trading volume in SPX box spreads topped $2.3 billion over the prior month, a 26% jump compared to the same period a year earlier. Even retail traders are getting in on the action, averaging $54 million in daily volume in the segment. A zero-coupon bond hiding inside an options trade For anyone unfamiliar, a box spread is a four-legged options trade: two calls and two puts at different strike prices, all on the same underlying index. When constructed properly, the trade’s outcome is completely predetermined regardless of where the market goes. Think of it as lending money with a guaranteed payoff at expiration, almost identical in function to a zero-coupon bond. The implied interest rate baked into that guaranteed payoff is where things get interesting. Three-month SPX box spreads are currently yielding north ...